There are many occasions where it is necessary to regenerate or otherwise restore computer video signals to their transmitted amplitudes. In one such instance, when analog VGA video and keyboard signals are routed between one of a plurality of computers and a single monitor and keyboard by switching equipment, such as the Commander module manufactured by Cybex Corporation of Huntsville, Ala., analog VGA video levels routed thereby may be reduced and high frequency components of the signal attenuated by switching circuitry inside the Commander module.
In another instance, where analog video and other data signals are coupled to or between workstations via relatively long conductors, similar signal losses occur. In order to compensate for these signal losses, it is generally necessary to regenerate voltage amplitude of the video and data signals prior to inputting them to a monitor and other peripheral devices. Typically, such regeneration is done by a pair of transistors coupled in a common emitter configuration, with the first transistor inverting the signal and the second transistor reinverting the signal in order to provide noninverted voltage amplification. While this type of amplifier requires power of a single polarity and ground, DC coupling of the amplifiers is generally difficult to implement and not particularly stable.
Accordingly, it is an object of this invention to provide a video and data regeneration circuit that is simple in construction and which possesses a voltage gain factor sufficient to boost a weak analog video signal to a conventional, usable amplitude.
Additionally, it is an object of this invention to provide a single transistor, noninverting, constant current voltage amplifier with controlled gain disposed to operate with a single polarity source of DC power with respect to ground and which is configurable to be a high frequency amplifier, a bandpass or tuned amplifier, a broadband amplifier, or a low frequency amplifier, each having a significantly high gain factor in their amplifying regions.